readline_completion_function() registers a callback that supplies tab-completion candidates for readline. This guide explains the function with focused examples and the decisions that matter in real applications.
What Is readline_completion_function() in PHP?
Registers a callback that supplies tab-completion candidates for readline.
A typical call looks like this:
<?php
readline_completion_function($callback);
The input arguments shown in the call identify the relevant connection, resource, value, path or configuration for the operation. Pay attention to argument order and to the return value demonstrated below.
Example 1: Basic Usage
This first example uses readline_completion_function() directly to demonstrate its basic purpose.
<?php
readline_completion_function(function (string $input): array { return ["help", "hello"]; });
The returned value illustrates registers a callback that supplies tab-completion candidates for readline. The callback should return an array of completion strings.
Example 2: A Different Input or Option
The next example changes the input or option, showing another supported use of readline_completion_function().
<?php
readline_completion_function(function (string $input): array { return array_filter(["list", "load"], fn($item) => str_starts_with($item, $input)); });
The returned value illustrates registers a callback that supplies tab-completion candidates for readline. The callback should return an array of completion strings.
Practical Example: Applying the Function
In application code, readline_completion_function() belongs in a controlled workflow with input validation, a checked result and cleanup where needed.
<?php
readline_completion_function(function (string $input): array { $commands = ["status", "start", "stop"]; return array_values(array_filter($commands, fn($command) => str_starts_with($command, $input))); });
The returned value illustrates registers a callback that supplies tab-completion candidates for readline. The callback should return an array of completion strings.
Important Behavior and Edge Cases
- Main behavior: Registers a callback that supplies tab-completion candidates for readline.
- Important limitation: The callback should return an array of completion strings.
- Requirements: This function uses the CLI readline extension; it is not designed for an ordinary web request.
Comparison With Related Functions
| Function or Approach | When to Use It |
|---|---|
readline_completion_function() | Registers a callback that supplies tab-completion candidates for readline. |
readline | Reads an interactive line of input from a terminal. |
Common Beginner Mistakes
| Mistake | Correct Approach |
|---|---|
Ignoring the specific limits or preconditions of readline_completion_function(). | The callback should return an array of completion strings. |
| Assuming every environment produces the same result. | This function uses the CLI readline extension; it is not designed for an ordinary web request. |
Key Takeaways
- Registers a callback that supplies tab-completion candidates for readline.
- The callback should return an array of completion strings.
- This function uses the CLI readline extension; it is not designed for an ordinary web request.
Use readline_completion_function() when its behavior matches your task, and verify the relevant return value before taking further action. The output depends on the local configuration when it uses resources, files or an interactive terminal.